simplepool.java

Tomcat 4.1与WebServer集成组件的源代码包.

/*
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 * The Apache Software License, Version 1.1
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 * Copyright (c) 1999 The Apache Software Foundation.  All rights
 * reserved.
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 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
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 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
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 *    if and wherever such third-party acknowlegements normally appear.
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 * This software consists of voluntary contributions made by many
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 * [Additional notices, if required by prior licensing conditions]
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package org.apache.tomcat.util.collections;

/**
 * Simple object pool. Based on ThreadPool and few other classes
 *
 * The pool will ignore overflow and return null if empty.
 *
 * @author Gal Shachor
 * @author Costin Manolache
 */
public final class SimplePool  {
    /*
     * Where the threads are held.
     */
    private Object pool[];

    private int max;
    private int last;
    private int current=-1;
    
    private Object lock;
    public static final int DEFAULT_SIZE=32;
    static final int debug=0;
    
    public SimplePool() {
	this(DEFAULT_SIZE,DEFAULT_SIZE);
    }

    public SimplePool(int size) {
	this(size, size);
    }

    public SimplePool(int size, int max) {
	this.max=max;
	pool=new Object[size];
	this.last=size-1;
	lock=new Object();
    }

    public  void set(Object o) {
	put(o);
    }

    /**
     * Add the object to the pool, silent nothing if the pool is full
     */
    public  void put(Object o) {
	synchronized( lock ) {
	    if( current < last ) {
		current++;
		pool[current] = o;
            } else if( current < max ) {
		// realocate
		int newSize=pool.length*2;
		if( newSize > max ) newSize=max+1;
		Object tmp[]=new Object[newSize];
		last=newSize-1;
		System.arraycopy( pool, 0, tmp, 0, pool.length);
		pool=tmp;
		current++;
		pool[current] = o;
	    }
	    if( debug > 0 ) log("put " + o + " " + current + " " + max );
	}
    }

    /**
     * Get an object from the pool, null if the pool is empty.
     */
    public  Object get() {
	Object item = null;
	synchronized( lock ) {
	    if( current >= 0 ) {
		item = pool[current];
		pool[current] = null;
		current -= 1;
	    }
	    if( debug > 0 ) 
		log("get " + item + " " + current + " " + max);
	}
	return item;
    }

    /**
     * Return the size of the pool
     */
    public int getMax() {
	return max;
    }

    /**
     * Number of object in the pool
     */
    public int getCount() {
	return current+1;
    }


    public void shutdown() {
    }
    
    private void log( String s ) {
	System.out.println("SimplePool: " + s );
    }
}